Tyre repair sealing composition

ABSTRACT

A tyre repair sealing composition having: 30 to 80% natural latex, 5 to 35% synthetic latex, and 10 to 60% ethylene glycol, and wherein the diameter of the synthetic latex particles advantageously has a mean particle-size distribution of 0.04 to 0.5 μm.

CROSS REFERENCE APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/076,984 filed Mar. 31, 2011, which is a continuation of U.S. patentapplication Serial No. 12,867,296 which is a 371 of InternationalApplication PCT/IB2008/003645 filed Dec. 30, 2008, which claims thebenefit of Italian Application No. TO2008A 000120 filed Feb. 18, 2008,the content of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a tyre repair sealing composition.

BACKGROUND ART

Tyre punctures are known to be repaired with sealing composition, whichis injected into the tyre to repair the puncture from the inside andmake the tyre airtight.

Various types of sealing compositions are known, in which a rubber,normally natural rubber, latex is mixed with adhesive and antifreeze.

Sealing compositions of this sort have the drawback, if kept for longperiods of time, of the latex and adhesive particles combining to form acreamy composition which, when dispensed, clogs the dispenser valve andfails to repair the puncture properly.

Research by the inventors has shown one reason for clogging of thedispenser valve would appear to be the large size—1 micron—and uneven,unstable size distribution of the natural rubber particles.

Compositions containing no adhesive are also known, but which alsoresult in clogging of the dispenser valve.

A need is therefore felt for a tyre repair sealing composition designedto eliminate the drawbacks of known compositions.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a sealingcomposition that is stable over time, and whose rubber latex particlesundergo no aggregation resulting in clogging of the dispenser valve.

BRIEF DESCRIPTION OF THE DRAWINGS

According to the present invention, there is provided a sealingcomposition as claimed in claim 1.

The present invention will be described with reference to theaccompanying drawings, in which:

FIG. 1 shows a comparison, relative to formula D described below(carboxylated synthetic latex and ethylene glycol), of a sample settledfor 48 hours in contact with air (test 9) and a sample settled for 2hours and tested immediately (test 10);

FIG. 2 shows a pressure-time graph of the 0% synthetic latex formula inExample 4;

FIG. 3 shows a pressure-time graph of the 10% synthetic latex formula inExample 4;

FIG. 4 shows a pressure-time graph of the 25% synthetic latex formula inExample 4;

FIG. 5 shows a pressure-time graph of the 50% synthetic latex formula inExample 4;

FIG. 6 shows a pressure-time graph of the 75% synthetic latex formula inExample 4;

FIG. 7 shows a pressure-time graph of a 5% synthetic latex formulahot-tested as in Example 5;

FIG. 8 shows a pressure-time graph of a 10% synthetic latex formulahot-tested as in Example 5;

FIG. 9 shows a pressure-time graph of a 15% synthetic latex formulahot-tested as in Example 5;

FIG. 10 shows a pressure-time graph of a 20% synthetic latex formulahot-tested as in Example 5.

BEST MODE FOR CARRYING OUT THE INVENTION

In a preferred embodiment, the synthetic latex has a mean particle sizeof 0.04 to 0.5 μm, and was advantageously used to manufacture a sealingcomposition. This formula provides for considerably stabilizing thesealing composition and so preventing particle aggregation, while at thesame time maintaining excellent sealing power characteristic ofnatural-latex-based compositions.

A synthetic latex particle diameter with a mean particle-sizedistribution of 0.05-0.3 μm was found to be preferable, and even morepreferable with a particle-size distribution of 0.1.

According to one aspect of the invention, the sealing compositionpreferably comprises 40 to 70% of natural latex, 10 to 20% of syntheticlatex, and 20 to 50% of ethylene glycol. More preferably, thecomposition comprises:

-   -   50-52% of natural latex    -   14-16% of synthetic latex    -   31-33% of ethylene glycol

The synthetic latex has a gelation rate, measured by Mallon mechanicalstability testing based on JIS-K6387, of preferably at least 25%, andmore preferably of over 50%, and is advantageously selected from thegroup comprising styrene-butadiene and carboxylated styrene-butadiene.

The natural latex used gave excellent results when deproteinized.

The sealing composition may also comprise 0.5-3%, preferably 1-2%, of apolyurethane latex, which has a further stabilizing effect.

Finally, the sealing composition may also comprise additives, such as anantioxidant, preferably in the amount of 0.05-3% and more preferably0.1-1.5%, and a stabilizing agent, preferably in the amount of 0.2-3%and more preferably 0.5-2%.

The present invention will now be described by way of a number of purelynon-limiting examples.

EXAMPLES Example 1 Chemical-Physical Characteristics

Various compositions were compared. While respecting the 3 to 2 latex toethylene glycol proportions (60% latex+40% ethylene glycol), numerousformulas were prepared, the composition of which is based on other thannatural latex; and tests were conducted on the following formulas:

-   -   Formula: Hartex 101 natural latex and ethylene glycol    -   Formula A: Euratex S3 and Euratex T22R pure natural latex from        Malaya with added non-ionic surface-active agents and ethylene        glycol    -   Formula B: Euratex S3 and Euratex T22R pure natural latex as        above with non-ionic surface-active agents and carboxylated SBR        in a 3:1 ratio and ethylene glycol    -   Formula C: Euratex 2007 softer-film styrene-butadiene (SBR)        latex and ethylene glycol    -   Formula D: Euratex 2007 harder-film (carboxylated)        styrene-butadiene (SBR) latex and ethylene glycol    -   Formula E: commercial formula prepared in the laboratory.

Though the actual commercial formula was also tested, formula E wasincluded in the tests to study the product in conditions independent ofstorage and transport-induced chemical-physical variations, which maystrongly affect a highly variable natural-latex-based product.

The results of viscosity testing the above formulas are shown below:

Temperature Viscosity Formula Latex (° C.) (mPa * s) A Natural n^(o)124.3 20.4 B Natural n^(o)2 23.8 20.3 C Synthetic n^(o)1 24.2 19 DSynthetic n^(o)2 23.8 18.7

No significant differences were observed between the viscosities of thenatural latexes (about 20.35 mPa*s) and synthetic latexes (about 18.85mPa*s). The lower viscosity of the synthetic latexes is closely relatedto their particle size, which particle-size analysis shows to be muchsmaller than for natural latexes. More specifically, values range fromabout 1 μm for natural latexes to one tenth of that, roughly 0.1 for thesynthetic latexes tested. Moreover, the synthetic latexes proved to havehighly defined particle-size distributions with well centred, very thinGaussians, indicating a large number of particles with the samediameter.

Example 2 Valve Injection Tests

The test system simulating the composition dispenser system comprised acompressor, a gauge, and a system for supporting the compositioncontainer. These were integrated with a pressure gauge and a flow gaugeto monitor pressure and flow throughout testing.

Injection of the composition through the valve was therefore tested bysimulating the operating conditions of a normal commercial dispensersystem.

When the compressor is activated, the composition is expelled from thecartridge and flows along the system's silicone tube, to the end ofwhich the valve is screwed. As soon as the composition in the cartridgeruns out, air is supplied to inflate the tyre. The composition expelledfrom the cartridges is collected in a container. The test lasts roughly5 minutes, which is more than enough to reach a final tyre pressure ofabout 2.5 bars (35 PSI).

Ambient-temperature injection tests were conducted of the compositionsin Example 1.

The best results were obtained from the synthetic-latex formulas (C andD) and the natural-latex formula B.

Example 3 Effect of Settling and Contact with Air

Testing was carried out using samples prepared at the time of testing,and the results were compared with those of the same compositionsprepared long before testing, to evaluate the settling effect on thesamples.

FIG. 1 shows the comparison, relative to formula D (carboxylatedsynthetic latex and ethylene glycol), of the sample settled for 48 hoursin contact with air (test 9) and the sample settled for 2 hours andtested immediately (test 10).

As with all the other tested formulas, the sample left longer in contactwith air produces a higher pressure peak at injection, and generallymaintains a higher pressure than the non-settled sample with no contactwith air.

A particular point to note is that, after injection, the carboxylatedsynthetic latex formula D produces no significant rise in pressure: afact that is of enormous advantage application-wise.

Example 4 Mixed-Composition Injection Tests

To achieve both troublefree injection in all types of valves andeffective, long-lasting repair, the composition has been found torequire both natural and synthetic latex. Given the excellent results offormula D in Example 1, the following compositions were first tested:

-   -   0% carboxylated synthetic latex (commercial latex)    -   10% carboxylated synthetic latex+90% commercial latex    -   25% carboxylated synthetic latex+75% commercial latex    -   50% carboxylated synthetic latex+50% commercial latex    -   75% carboxylated synthetic latex+25% commercial latex.

As shown in FIGS. 2-7, the best performance was obtained from mixtureswith a synthetic latex percentage ranging between 10 and 250. Despitethe tendency, typical of the type of synthetic latex tested, ofmaintaining more or less constant pressure after injection, the range ofcompositions examined show lower, and therefore more desirable, minimumvalues. Generally speaking, all the mixed compositions give betterresults than the commercial formula: both the peak pressures and thepressures during repair are lower, and injection itself is faster(narrower injection peak).

Example 5 Hot Injection Tests

The procedure adopted for these tests is the same as forambient-temperature testing in Example 2, except that the sample isheated for 1 hour at 70° C. before testing.

As shown in FIGS. 8-10, the results show good performance of the mixedcomposition with 15% carboxylated synthetic latex.

As compared with ambient-temperature testing, hot testing generallyrecords lower injection pressures (lower peaks).

Example 6 Road Tests

The formulas selected above were actually road tested on various typesof tyres: winter, summer, symmetrically-grooved, asymmetrically-grooved,and in substantially two different situations: punctures in which theobject remains embedded inside the tyre, and punctures in which theobject is extracted. In the first case, the nails used to puncture thetyre were left in during repair; and, in the second case, the car wasrun over a steel plate to puncture the tyre and automatically free thehole. In both cases, the nails used were 6 mm in diameter.

The punctured tyre was then repaired using the dispenser system (eachtime with a cartridge of the desired composition) and covering the arearecommended in the handbook to ensure effective repair. In addition tobeing monitored throughout the test, tyre pressure is checked aftertesting and again after 24 hours to detect any failed repairs notdetected at first.

The best injection test results were obtained from formulas B, C and D.The gauge readings were recorded alongside stopwatch time recordings.

Formula D showed the best performance application-wise, with fairlynarrow injection pressure peaks and much lower maximum values than theother two cases, and even the pressure increase after injection was muchmore gradual, thus indicating a not too excessive rise in pressure, i.e.the composition flows smoothly into the tyre through the valve, evenduring normal use of the kit.

Example 7 Mixed Composition Road Tests

As for valve injection testing, road testing was also conducted ofcompositions with a percentage of synthetic latex ranging between 5 and20%. The results also confirm the greater effectiveness in terms ofrepair of the mixed composition with 15% carboxylated synthetic latex.

Generally speaking, all the repairs made using mixtures with syntheticlatexes were successful, and the various tyre pressure recordings werestill constant 24 hours after repair. Repair is slightly faster usingthe 15% synthetic latex mixture, on account of the faster injectionstage (narrow peak), which means actual repair (air flow into the tyre)occurs sooner than in the other cases analysed.

1. A tyre repair sealing composition comprising: 30 to 80% natural latex5 to 35% synthetic latex to 60% ethylene glycol.
 2. A sealingcomposition as claimed in claim 1, characterized in that the diameter ofthe particles of said synthetic latex has a mean particle-sizedistribution of 0.04 to 0.5 μm.
 3. A sealing composition as claimed inclaim 2, characterized in that the diameter of the particles of saidsynthetic latex has a mean particle-size distribution of 0.05 to 0.25μm.
 4. A sealing composition as claimed in claim 2, characterized inthat said diameter of the particles of said synthetic latex has a meanparticle-size distribution of 0.1 μm.
 5. A sealing composition asclaimed in claim 1, characterized by comprising 40 to 70% of saidnatural latex.
 6. A sealing composition as claimed in claim 1,characterized by comprising 10 to 20% of said synthetic latex.
 7. Asealing composition as claimed in claim 1, characterized by comprising20 to 50% of said ethylene glycol.
 8. A sealing composition as claimedin claim 1, characterized by comprising: 50-52% natural latex 14-16%synthetic latex 31-33% ethylene glycol.
 9. A sealing composition asclaimed in claim 1, characterized in that said natural latex is adeproteinized natural latex.
 10. A sealing composition as claimed inclaim 1, characterized in that said synthetic latex is selected from thegroup comprising styrene-butadiene and carboxylated styrene-butadienelatex.
 11. A sealing composition as claimed in claim 1, characterized bycomprising a polyurethane latex.
 12. A sealing composition as claimed inclaim 5, characterized by comprising 0.5% to 10% polyurethane latex. 13.A sealing composition as claimed in claim 5, characterized by comprising1% to 4% polyurethane latex.
 14. A sealing composition as claimed inclaim 1, characterized by comprising an antioxidant and a stabilizingagent.
 15. A sealing composition as claimed in claim 8, characterized bycomprising 0.1-1.5% of said antioxidant, and 0.5-2% of said stabilizingagent.
 16. A sealing composition as claimed in claim 1, characterized inthat said synthetic latex has a gelation rate, measured by Mallonmechanical stability testing based on JIS-K6387, of at least 25%.
 17. Asealing composition as claimed in claim 10, characterized in that saidsynthetic latex has a gelation rate, measured by Mallon mechanicalstability testing based on JIS-K6387, of over 50%.